Boiler Aquastat & Power

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  #1  
Old 02-20-17, 07:16 AM
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Boiler Aquastat & Power

So I had a contractor add a 2nd pump and stat to my hot water heat system in order to go from 1 zone to 2 zones. Afterwards, he noticed that the boiler/aquastat on/off is tied to the original pump & stat. In other words, the boiler is fully off unless Zone 1 calls for heat. So if Zone 2 calls for heat, the pump kicks on but just circulates cold water around.

He said this is uncommon, and that typically the aquastat keeps the water in the boiler at 180 regardless of whether the system is calling for heat, similar to a water heater. His solution is to bypass the switch so that the boiler is always powered and always keeping water at 180, and the pumps can operate independently to circulate the 180 water.

I'm looking for a second opinion on this site: Is it typical (as he says) to have the boiler on at all times, regardless of the system calling for heat or not? Seems wasteful of energy to keep the water in the boiler hot. I feel like the best solution is that the boiler kicks on when either stat calls for heat, but perhaps that wiring solution is more complex than I imagine.

Any thoughts on this? Thank you.
 
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Old 02-20-17, 09:01 AM
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pasc

Im not one of the experts here, but what that guy says seems totally wrong to me. You dont need to keep the water hot all the time. Cold start boilers heat the water when needed. I think you are supposed use a controller something like the SR502 which according to the description:

Operation:
When the thermostat calls for heat, the appropriate circulator is energized and the isolated end switch (X1and X2) will start the boiler.
You can see the hookup on the left figure here:

http://www.taco-hvac.com/uploads/Fil...2(102-082).pdf

Well see what the knowledgeable guys say, Im sure they will be around.
 
  #3  
Old 02-20-17, 09:10 AM
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p,
It is not common for a boiler to maintain temp 24/7 unless you have a tankless coil for domestic hot water. He is setting you back 30 years not to mention wasted fuel. What was his answer for summer be except to shut the boiler completely off.

What you need is a separate switching relay like a Taco SR501-4 or a Honeywell RA845A. There are others also you can use.

You can also get a Taco multiple zone control panel where everything is brought into one box for convenience, but in your case at a price. If you are not going to add anymore zones the single relay will do just fine.

One thing to check for first is to see if your currant aquastat has a ZC & ZR terminals on it and when wiring the new relay use those terminals or the burner will not come on to reheat the water when your new zone calls and you'll be in the same boat. The way the relay is wired means everything for proper operation.

Hope this helps a little
 
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Old 02-20-17, 09:22 AM
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I should have thought of that because that’s exactly what I have:

2 zones with the R845A used to control Zone 2 connected to ZC/ZR on the L7224U Aquastat.

whoops! forgot to say my water is in fact hot all the time because i have a tankless coil. OK i'll stop muddying the waters!
 

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  #5  
Old 02-20-17, 10:14 AM
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Z,
Please keep muddying. You keep me thinking. Look forward to your thoughts. You seem to enjoy yourself and do put a lot of thought and common sense into your solutions.

Be well
 
  #6  
Old 02-20-17, 10:46 AM
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Thanks for responses. I'll reply below.

What was his answer for summer be except to shut the boiler completely off.

There is an existing outdoor temperate sensor (not an outdoor air reset) that cuts power over the set outdoor temperature, though it wasn't working when tested. Which never mattered before, since the power to the aquastat was tied to the thermostat anyways. In theory, any outdoor temps over 65 should turn off the aquastat.

If you are not going to add anymore zones the single relay will do just fine.

The SR502 Wiring Diagram seemed more straightforward to me, so that I understand. Any (up to 3) zones trigger the aquastat, and the associated circulator pump. Straight forward wiring.

For $70 the R845A ischeaper but to your point, Zone 1 is still wired directly into the aquastat. The R845A isn't a central control box. Are the ZC and ZR just used to trigger alternate inputs to turn on the boiler?

Last, but not least, the most important question. We're in a warm spell and I want to be sure my heat is working. I may do the wiring myself in the summer, as I am not in love with this contractor anyways. I'm no electrician but this wiring doesn't seem overly complicated.

Is there any harm or risk for the aquastat to be forced on for the rest of the winter? I understand keeping the water at 180 is wasteful. Are there any other concerns?
 
  #7  
Old 02-20-17, 11:33 AM
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What do you have for an aqustat and what switch is he planning on bypassing and also how is he planning to run the zone 1 pump once he bypasses the switch to maintain boiler temp.
 
  #8  
Old 02-20-17, 12:04 PM
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I'll have to check model numbers tonight. Assuming he gets his "always on" version to work, are there any concerns about leaving it as is until summer? I don't want to risk rewiring the whole system during winter.
 
  #9  
Old 02-20-17, 12:17 PM
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I don't recommend jury rigging anything but with that being said how did he hook up your zone 2 pump. Does it come on with a tstat.
 
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Old 02-20-17, 12:24 PM
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Yes, the zone 2 pump turns on just fine with the stat. It's just that the boiler doesn't fire on unless zone one goes. Zone 2 is wired back to the aquastat, it just isn't firing.
 
  #11  
Old 02-20-17, 12:48 PM
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Do you have pics of the wiring in aqustat. What does he have the pump tied into.

If you are not going to fix this now, what I'm getting at is if you are going to do it your way can you duplicate zone 1 pump the way zone 2 is wired and just put a jumper across TT on aquastat. That will act as if a stat is always calling and the boiler will shut down at 180 and come back on when the boiler temp drops a nd the 2 pumps will run when the stats call and you won't have to rewire anything keeping the safety's intact.

The only thing you will have to do is remove Z1 pump wire from C1 & C2 and duplicate the way he has Z2 pump.

Just a thought.
 
  #12  
Old 02-20-17, 01:03 PM
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He is coming by to finish the wiring tomorrow. I will figure out what he does and come back here so I don't mislead you. Right now, the zone two pump is just pumping cold water.
 
  #13  
Old 02-20-17, 01:10 PM
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It's only pumping cold water because there is no wire going to TT from that zone to complete the circuit and turn on the boiler. You could run your pump directly from any 110V source and do the same thing. That is where the relay comes in. Your pump is 110 and your stat is 24V. The relay separates the two and allows you to activate TT when the zone calls.

In order for your stat to activate the pump he had to use a transformer somewhere because of the 2 different voltages.
 
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Old 02-21-17, 09:52 AM
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Alright, here's the photos and data. The new thermostat 2 is wired to a relay and transformer to run the new pump 2.

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This power source is coming directly from the main boiler control switch, NOT the aquastat. So the new thermostat is not wired to the aquastat at all. Hence the problem.

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As the next two photos show, there is a relay and transformer to let the thermostat turn the pump on and off.

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He is coming by tomorrow and I think his plan is to force aquastat always on because he plans to buy another relay to have Thermostat 1 only control Pump 1, not Pump 1 & Aquastat. So it will basically become a hot start boiler.

There is an existing outdoor air sensor tied to the aquastat that turns it off when outdoor air is over the set point (say, 65) to address energy savings in summer. He says it's not worth the $100 for the relay or control box to make the boiler a cold start, because leaving the aquastat on all the time barely uses any natural gas. Though I tend to disagree (and I believe you disagree too?).

Comments welcome, but since a cold snap is coming, I think I'm stuck with a hot start boiler until summer when I can rewire this myself. Thoughts & comments? Your help is always appreciated. Thank you.
 
  #15  
Old 02-21-17, 11:43 AM
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Are you saying he is going to alter the wiring from zone 1 to install the pilot control relay. Pardon my bluntness but that is the most incompetent and senseless thing I have seen in a long time, and all to make your boiler into a warm start to get your boiler to start when Z2 calls.

Generally when you add a zone it's to have better control of your heat and where it goes. I basically said all I have to on the subject in post 13.

Besides doing you a disservice this guy is making all kinds of needless work for himself which you will end up paying for and changing later.

By the way, he did a great job tying into that service switch box. I hope it's not going to stay like that. I would love to see the look on an inspectors face when he saw that. Do yourself a favor and lock the door when you see this guy coming and get someone who has a clue.

Sorry for the rant but I can't believe anyone with a license could do this type of work.
 
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Old 02-21-17, 12:07 PM
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I'm not sure of the terminology or how he's wiring it - he's just making the boiler a warm start so each thermostat only triggers pumps, not the aquastat, which will be always on.

I'll probably be back here come summer for advice so I can wire a control box or relay myself.

also I'm sure he's closing the service switch box when he returns- that's not ok to leave.
 
  #17  
Old 02-21-17, 03:07 PM
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p,
Just a word of advise. If you plan on trying to fix this later by yourself mark the wires or take video of what he does because to do it correctly everything will have to get put back and those pilot relays he's using eliminated before you wire the new switching relay or Taco panel.

Hope this works out for you for now.
 
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Old 02-21-17, 03:46 PM
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Funny, I was writing to say the same thing! I'm going to snap a bunch of photos tonight so I at least know what my starting point is before work is complete. Sounds like the consensus here is that his idea is not good, but also not dangerous. To do it right, I should be using a relay or Taco panel to keep my boiler as a cold start.

Based on what I can tell, he's installing a new rib relay tomorrow so that Thermostat 1 can be wired directly to control Pump 1, and not go to the aquastat TT terminals at all. I bet he's planning to jump the TT terminals just as you suggest. Thanks for help. I'll post an update once I understand exactly what he did, just in case it's a truly terrible idea.
 
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Old 02-21-17, 04:03 PM
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p,
I'll be waiting to hear.

Good luck,

Skip
 
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Old 02-22-17, 09:59 PM
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Update

Ok, here goes. His work is done, but his work was obviously not the solution. Previously I mentioned the outdoor air temp sensor - he wired that to the aquastat's thermostat terminals to trigger aquastat always on for outdoor air temps under 60.

Problem 1: the hot boiler water is naturally circulating even though the t stats and pumps are off, drastically heating the house because it's 58 out and the aquastat is on. I turned the sensor down to 55 because the house was way too hot. He thought the pumps, when off, would impede flows. This is not happening. Solution: taco control box or relay.

Problem 2: he said pumps would mostly impede flows and is using them as check valves. Will this work if 1 pump is on? I am concerned that my cold zone will pump much longer and simply overheat the already hot zone. I'll test this out in cold weather, which may be awhile. Solution (if needed): add zone valves.

Thoughts?
 
  #21  
Old 02-23-17, 09:09 AM
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Sorry, one edit. For problem 2, the solution (if needed) is to add check valves, not zone valves. Both pumps appear to have internal check valves already, though. If this is the case, how is hot water naturally circulating around the system and heating rads even with pumps off?
 
  #22  
Old 02-23-17, 10:22 AM
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p,
If the pumps have IFC installed and are working the water is not able to flow. If the pumps are on the return you may get a little hot water going up the supply but should never reach the emitters.

Did he remove Z1 pump wires from C1 & C2. If they are still connected then when TT calls the pump will run even though your stat is not calling.

Any chance of more pics of the boiler shot from far enough to get the piping and controls in and a little of the supply piping with valves if any.

One more thing about your pump question. If they do in fact have check valves, the only way to open those valves is from the flow the pump creates so they do act independently and one does not effect the other. That is the sole purpose for their installation.

Are both zones getting hot or just one after he did the work.
 
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Old 02-24-17, 11:04 AM
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All, thank you for the help. I have a taco two zone control box ready to go. However, I do need some wire to run to the TT terminals from the control box to control the aquastat . What gauge wire is appropriate?
 
  #24  
Old 02-24-17, 12:14 PM
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p,
Use regular t-stat wire which is 18 gauge. For your purpose 18/2 is fine. If you get some with more wires just don't use extra but you will have them in case of changes.
 
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Old 02-24-17, 12:39 PM
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Excellent. The control box is going to be easier than expected as all of the power and thermostat wires are already in one place. I will just be moving them from his crazy relay set up to the control box. I will leave adding flow check valve to the experts.
 
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Old 02-26-17, 09:41 PM
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Well, project complete! Almost. The taco control panel works great, and it was relatively simple to move all the wires to the new control box. Such a clean set up compared to what I had. Only one hiccup. Part of his elaborate set up included jumping a transformer off the pump power line to provide constant 24 V power to the C terminal on the new thermostat. I took that power source away to power the new control box so the stat has no power. I can run new 120v to the transformer to step down to power the thermostat, but even writing that makes it seem like a very odd solution. Is there a better one?
 
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Old 02-27-17, 07:37 AM
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Been thinking about this more - wondering if that really is the easiest solution. Just run a new 120V line from a nearby box to the transformer (already mounted with a box, already wired for the C wire) and be done with it. It feels odd to have dedicated 120V just for the C wire, but my aquastat doesn't have a C terminal so this may be the most simple (and easy) way to go. Still open to other ideas! You guys have been so helpful to date.
 
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Old 02-27-17, 07:56 AM
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p,
In your taco relay you have 2 terminals in the upper left marked 24v and C. Use the C terminal to connect to C on the stat and that should do it.
 
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Old 02-27-17, 08:36 AM
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Ah. Obviously. It all just clicked in my head. Are both terminals in the upper left 24 V so I could run two C wires for two thermostats? I assume so, because Taco obviously took the time to lay out and label this control box intelligently.

I ask because I will upgrade my other Thermostat this year and it doesn't have a C wire either. This is the obvious 24V supply source for when I do.

Thanks for putting up with all my questions. I've never wired or investigated my boiler control system before, so I'm basically learning everything from you guys.
 
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Old 02-27-17, 09:55 AM
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p,
You only use the C terminal to the C terminal on the stats. If you have 2 stats you can run off of that same C terminal. The 24v terminal is for something different. Another story, but you do not want to use that terminal, just the C.
 
  #31  
Old 02-27-17, 10:06 AM
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p,
If you are curious those terminals are the same as a 24v transformer but is only rated as a 15va transformer where a common 24v would be a 40va rated so there is a limit as to how many stats you can connect depending on your stat watts rating but 2 should be fine.

The 24v side is the same as the other side of a transformer to go to a gas valve for example but nothing that pertains to you at this point.

Hope this helps.
 
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Old 02-27-17, 10:29 AM
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Makes sense to me. Good thing I didn't wire into the 24 VAC! I'll check the draw of my thermostats to be sure I stay under the 15va before installing the 2nd one.

So, out of personal curiosity, is the thermostat actually drawing the 24v from the red or white wire in this scenario, and just using the C to complete the circuit?
 
  #33  
Old 02-27-17, 10:55 AM
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There is a 24v transformer built into the relay to power your stats initially for 2 wire stats. The one you're going to use for the C term. is an extra trans. for that purpose. It is doing the same as you were going to do by bringing power to that trans. you had to bring power to the C on your stat but they have added it for the new stats that require it. If you look at the ZV relay boxes from Taco they have the 3 terminals for each stat. The SR relays which you have do not and before you ask, I don't know why.

I hope this answers your question.
 
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Old 02-27-17, 10:58 AM
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If you use a separate transformer to run the stats.... you need to connect the power to Rc and C on the stats. There should be no jumper between Rc and Rh.

The heat connects to W and Rh.

The stat draws its power from the R terminal and sends switched 24vac back on white.

The C connection is ONLY to run the stat electronics. Nothing else.
 
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Old 02-27-17, 11:03 AM
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I started to write something and got interrupted but I think PJ answered the question.
 

Last edited by spott; 02-27-17 at 11:20 AM.
  #36  
Old 02-27-17, 01:22 PM
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I'll be able to avoid using the separate transformer to run the stats, but great explanation anyways. I'll connect the Comm in the Taco SR502 to the C terminal tonight. That "should" be it. Thanks for all the education.
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